Apparatuses are known for bending metal products, also called stirrup-making machines, configured to bend a bar, a round piece, a metal wire, or other oblong metal product, in order to make stirrups for reinforcement cages.
The reinforcement stirrups can be two-dimensional stirrups, that is, whose sides lie on the same plane, or three-dimensional, in which at least one side lies on a different plane from that of the other sides. This angled side can have, for example, the function of a spacer or reference, with respect to another stirrup or to an existing structure.
Apparatuses are known for three-dimensional bending comprising a drawing unit, a shearing unit and a first bending unit that makes the bends on a first bending plane, in order to define the two-dimensional shape of the stirrup. This known apparatus also comprises a separate and subsequent second bending unit that makes the bends on a plane angled with respect to the first bending plane. The first bending unit consists of a bending support, or rotating mandrel provided centrally with a contrast pin and radially with a bending element.
The bending element can be rotated either clockwise or anti-clockwise, around the contrast pin, so that the segment of metal product that is interposed between the bending element and the contrast pin is bent around the latter.
In the same way, the second bending unit, distanced and autonomous with respect to the first bending unit, provides a contrast member disposed distanced from the feed plane of the metal product, in order to allow the latter to interpose itself between the contrast member and the feed plane.
The bending element is mobile on exit from the feed plane so as to intercept and plastically deform a segment of the metal product around the contrast member.
This type of known bending apparatus, providing two separate bending units, needs a double command and control line, both mechanical and electronic, to guarantee the management and operating coordination of the two bending units. This management requirement causes an increase in the times and costs of producing the apparatus, as well as time and maintenance costs of the latter. Moreover, having two separate bending units, the number of mechanical components that participate in the individual movements is also high. In the light of this, the known apparatus is bulkier than traditional two-dimensional machines and because of this, both the minimum dimension of the stirrup that can be obtained and also the precision of the bending can be compromised.
An apparatus is also known of the general type as described above for bending metal products with a two-dimensional and/or three-dimensional mode, described in the document WO2011/064222, in which the bending pin is also provided with a shaped portion that defines, in its turn, a contrast element for bending the metal product on a second bending plane, substantially transverse with respect to the first bending plane.
In particular, the shaped contrast portion is located above the feed plane of the metal product so as to define with it a hollow space through which the metal product is made to pass.
Immediately downstream of the first bending unit a bending member is provided which is selectively movable in a direction transverse to the feed plane of the metal product, so as to intercept and plastically deform the metal product and bend it on a plane substantially orthogonal to the first bending plane.
In particular, the movement of the bending member determines the bending of the metal product around the shaped contrast portion of the bending pin of the first bending unit.
Although it reduces the complexity of management and command of the different mobile components, this solution is also excessively bulky and has high production costs.
Moreover, the particular conformation of the shaped contrast portion of the bending pin makes the latter bulky and in some applications it interferes with the normal operations of two-dimensional bending.
One purpose of the present invention is to make an apparatus and perfect a method for bending metal products that allow to produce both two-dimensional stirrups and three-dimensional stirrups, that have limited times and costs, of production, management and coordination, and that provides simplified maintenance steps.
Another purpose of the present invention is to make an apparatus for bending metal products that allows to make both two-dimensional stirrups and three-dimensional stirrups, that has limited bulk when installed compared with similar known bending apparatuses and that guarantees an optimal bending precision.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.